Description

Setting the following in portlet.xml
<container-runtime-option>
<name>javax.portlet.actionScopedRequestAttributes</name>
<value>true</value>
</container-runtime-option>

should enable any attributes set into the portletRequest during the action phase to be available in the render phase, and subsequent render calls until another event/action method is called.

Currently setting a portletRequest attribute in the action phase with this property set, does not make the attribute available on subsequent calls to render. So the key issue here is that when the portlet container tells the portlet that it needs to re-render, usually as a result of a user interacting with another portlet on the page, then the request attributes are lost.